基于碳碳键与自由基动态可逆平衡的本征型结构用自修复聚合物的构建

Mechanical strength of the currently reported intrinsic self-healing polymer materials is too low to be using as structural materials. In order to overcome this disadvantage, the aromatic pinacol monomers with both higher bond energy and dynamic thermal reversible properties are synthetized by radiation of benzophenone derivatives, and then introduced into macromolecular chains cross-linking by multifunctional monomers. The bond energy and homolytic temperature of central C-C bond are regulated by changing the steric effect and electronic effect. Upon heating to a certain homolysis temperature, reversible dynamic fission-recombination properties of the center C-C bond could be activated, achieving intrinsic self-healing of cracks. On the other hand, molecular structure of the materials remain stable at ambient temperature owing to the dormancy of C-C bond, which could avoid the rapid stress relaxation due to reversible exchange of dynamic bonds and also provide higher mechanical strength. Compare with intrinsic self-healing polymer based on DA bond, the dynamic reversible C-C bond could achieve healing at a single temperature without damage the structure of materials rather than at two different temperatures. Further, the project will explore a new method for solid-state recycling and processing of the crosslinking polymer materials through the exchange and recombination of dynamic covalent bonds, which could solve the defects of traditional depolymerization technology of recycling such as high energy consumption and environment pollution. Owing to the solid period research foundation, fully pre research, prominent innovation and high feasibility, the project has important theoretical and practical value for the development and application of new self-healing polymer materials.

为克服目前报导的本征型自修复高分子材料普遍存在强度低、不适合作为结构材料使用的缺点，本项目拟采用二苯甲酮衍生物，经紫外光照合成芳香片呐醇单体，利用空间位阻效应和电子效应调节其中心C-C共价键的键能和均裂温度，使该C-C键兼具较高键能和动态热可逆结合性，进而通过功能基团将其引入交联高分子材料。当加热到一定温度时，片呐醇中心C-C键的动态可逆断裂－结合特性得以激活，相关高分子材料即可实现裂纹的本征自修复，而在常温环境中，由于动态可逆C-C键处于休眠态，材料的分子结构保持稳定，避免了因动态键可逆交换引起的迅速应力松弛，并且C-C键赋予材料较高的强度。进一步，将探索利用动态共价键交换重组进行交联高分子材料固态循环加工的新方法，解决传统解聚回收技术的高能耗、污染环境等问题。本项目的前期研究基础扎实，预研充分，创新性突出，可行性高，对于发展新型自修复高分子材料及其应用，具有重要的理论和实际价值。

为克服目前报导的本征型自修复高分子材料普遍存在强度低、不适合作为结构材料使用的缺点，本项目采用二苯甲酮衍生物，经紫外光照合成具有普适性和高扩展性C-C键的芳香片呐醇单体，利用空间位阻效应和电子效应调节其中心C-C共价键的键能和均裂温度，使该C-C键兼具较高键能（167.0 kJ/mol）和动态热可逆结合性（交换反应活化能为103 kJ/mol），进而通过功能基团将其引入交联高分子材料，并结合硬嵌段的氢键相互作用和软嵌段的结晶微区物理交联点，制备了一类具有优异机械强度的动态可逆“活性”交联聚氨酯，其拉伸强度和断裂伸长率可以分别在27.3~115.2 MPa和324~1501%之间灵活地调节。当加热到一定温度时，片呐醇中心C-C键的动态可逆断裂－结合特性得以激活，相关高分子材料即可实现裂纹的本征自修复，而在常温环境中，由于动态可逆C-C键处于休眠态，材料的分子结构保持稳定，避免了因动态键可逆交换引起的迅速应力松弛，并且C-C键赋予材料较高的强度。进一步，利用动态共价键交换重组进行交联高分子材料固态循环加工的新方法，碎片式破坏的聚合物材料在热可逆温度以上热压一定时间后，可以获得与原始样弹性模量相近的回收样品，解决了传统解聚回收技术的高能耗、污染环境等问题。最有意义的是，通常只适用于热塑性聚合物的固态拉伸取向增强技术，发现也可用于提高动态交联聚合物的力学性能，为改善动态交联聚合物普遍较低的力学强度提供了一种新的途径。此外，芳香片呐醇中心的C-C键在热或者紫外光照射条件下均裂产生的自由基可以引发乙烯基单体聚合，可方便地原位改性聚合物的表面和基体，获得可再生的表面图案和互穿聚合物网络等。相关研究思路未见报导，对于推动本征自修复材料的基础研究和实际应用具有重要价值。